The benefits of tuning a stock vehicle for the race track can be huge. Best of all, adjustments to your car's tuning do not affect your car's class rating. Since these changes don't affect your class rating, you can use tuning to improve the performance of your vehicle beyond the limits of your competition.

Tires

Adjusting your tire pressure is a good, simple way to improve the cornering performance of your vehicle. Stock tire pressure is generally tuned for comfort rather than raw conering ability. When you take a new vehicle to the track, you should always make some adjustments to the tire pressure, usually increasing the pressure to all four tires to improve responsiveness and reduce tire roll in the corners.

However, take note that too much inflation can give you the opposite effect. An over-inflated tire will bow out in the center, reducing the contact surface. This effect is maximized as the tires heat up and the air inside expands, increasing the psi level. If you've reached the effectiveness limit of inflation, try reducing tire pressure to similarly affect the grip levels of your tires. If your FWD car is understeering, especially as the race wears on and the tires heat up, lower the front tire pressure to keep the contact surface flat.

Lowering tire pressure gives the tire more pliability, allowing it to conform to the ground and increase the overall contact patch with the asphalt. Accordingly, lowering tire pressure can help straight acceleration. But low pressure comes with negative side effects that become evident during cornering, as the more pliable tire rolls under lateral acceleration and gives you sloppy handling.

One thing to remember is that a little adjustment goes a long way. Differences of just a few psi between wheels can have a big effect, so don't get extreme with the adjustments.

Gearing

Default, conservative gear ratios. Note the smooth curve of the line connecting the ratio graph bars.

Gearing ratios determine how many turns of the driveshaft result in a single turn of the wheels (the car's wheels, not your steering wheel). A higher ratio (e.g. 3:1) makes it easier for the engine to rev high and reach max horsepower output quickly, but minimizes the top end speed of the gear. The effect of high gear ratios is quick acceleration with a sacrifice to top speed. A low gear ratio (e.g. 0.8:1) is harder for the engine to turn but improves top-end speed in that gear. The effect of a low ratio is slow acceleration with high top speed.

Lower gears should have higher ratios, while higher gears should gradually move to lower ratios. Sudden drops in the ratios between gears (e.g. having a first gear ratio of 3:1 and a second gear ratio of 1:1) will make it difficult to keep your engine revving within its peak power band. Most engines make the most power in the upper limits of their rev range (like between 4,000 RPM and 6,500 RPM). If the jump between two gear ratios is too large, your engine will drop too many revs on the upshift, dropping below the optimal powerband. This drop in revs will make for slow acceleration until you can muscle the revs back to their peak power.

Imagine a curved line on the gearing graph that connects the right edges of the ratios for each gear. A gradual curve will make it easier to keep your engine revving within its optimal RPM range. However, a curve too dull will restrict the range of your gear ratios. A sharper turn will naturally give you more range between gear ratios, but as we mentioned earlier it may also cause the engine RPMs to drop too much between upshifts. Experiment with your car to find its peak power band and adjust the gears to keep your revs within that RPM range while giving you the acceleration or top speed you need for a given track.

This gearing is set for quick acceleration but low top-end speed. The tightly spaced gear ratios will keep the engine revving at its peak, but limits the range of each gear.

The low ratio of sixth gear makes for high top-end speed, but the large jumps between gear ratios may drop too many revs between upshifts, slowing acceleration.

Many tracks will not allow you to reach the maximum speed of your vehicle. In these cases, it's a good idea to increase your gear ratios to improve your acceleration. Other tracks, however, are all about top speed. On these tracks, it's worth sacrificing some acceleration by lowering your gear ratios to make for better top-end speed.